Stitch adjusting device for sewing machines



July 22, 1958 c. J. M. BENINK ET Al. 2,844,114

STITCH ADJUS'IINC DEVICE FCR SEWING MACHINES Filed Sept. 10, 1956 3Sheets-Sheet l Fig. 1

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July 22, 1958 l c. JQM. BENINK ET AL 2,844,114

sIIIcEADJusTING DEvIcE FOR SEWING MACHINES Filed sept. 1o, 195e ssheets-sheet 2 l/VVENTOBS STITCH ADJUSIING DEVICE FOR SEWING MACHINESFiled sept. 1o; 195e A C. J. M. BENlNK ET AL July 22, 195.8

3 Sheets-Sheet 3 United States -Patent f g 2,844,114 ce Patented Julyzz,195s sTrrcH ADJUsTlNG nEvIcE Fon SEWING MAcHlNEs Christiaan JosephMarinus Benink and Herbert Wenz,

Kaiserslautern, Pfalz, Germany, assignors to G. M. Pfaff A.G.,Kaiserslautern, Pfalz, Western Germany The invention relates to sewingmachines and particu-s larly to the mechanism for adjustingthe length`of the stitches produced by the machine. Y i

More in particular, the invention relates to a stitch length adjustingmechanism for sewing machines provided with a contact lever which, byswinging between` two curved edges which define the limits of anaperturek in a rotatable disk, provides'for the same stitch length forthe forward and the back stitch.

The invention is based on a mechanism having a contact lever which byreciprocating between two curved edges which dene the limits of a cavityin a turnable disk provides for the same length of the forward stitchand the back stitch, in particular by the coaxial arrangement ofthe diskwith the stitch'setting shaft andby continuous curves which are innonsymmetric relationship', the radial distances of which from the axisof rotation of said disk relative to av central neutral line areinversely related to each other. At the same time, the contact edgesprovide an accurately operating device which is directly andcontinuously adjustable in accordance with the markings, which requiresmerely a single, brief, readily executed setting operation to enablesewing immediately in accordance with the adjusted stitch in bothdirections.

Suitably a stop which is secured to the contact leve and which projectsinto the aperture of the disk is spring biased and continuously engagesone of the two curved edges.

The swinging movement of the contact lever is effected by an adjustmentmember, which is secured upon the stitch setting shaft, into the trackof operation of which extends a pin which is mounted upon the contactlever.

The stitch setting shaft is subject to the tension of a spring whichholds the arm in inoperative position when the handle is released.

It is an object of the invention to provide a stitch adjusting mechanismwhich is simple to operate and which is made of components which areeasily produced.

It is a further object of the invention to provide a stitch adjustingmechanism which requires particularly little space and which is simpleto operate by virtue of the fact that the disk is mounted upon a hollowshaft which is journalled in the wall of the housing and which, in turn,receives the stitch setting shaft.

Other objects and advantages of the invention will become apparent whenreference is had to the following description of an embodiment of theinvention which is illustrated in the accompanying drawings in which:

Fig. 1 shows a front view of a sewing machine which is provided with thenew stitch adjusting mechanism;

Fig. 2 is a cross-section of the machine taken through the mechanismalong line II-II of Fig. 1;

Fig. 2a is a cross section taken from the right hand side of Fig. 2showing the shaft, cams and connecting bars;

Fig. 3 is a partial sectional view taken along line III--III in Fig. 2,and

Fig. 4 is a partialA sectional -view taken along line IV-IV in Fig. 3. Yt

Fig. 1 illustrates the sewing machine which consists ofL the base plate1, standard 2,arm 3 and head 4. The arm shaft or main shaft 5 isrotatably journalled inthe arm of the machine in the usual manner andcarries the.'` balance wheel 6 at the end which projectsv from thestandard 2'. The mainshaft furthermore supports thevstitch setting cam 7(Fig. 2) which is in operative engagement with rthe bifurcated camfollower vbar 8, the end of which is joined to the crank 9, which inturn is clamped onto," the feeder advancing shaft 11 journalled inbearing lugs 10 (only one of which is'shown). `i n A sliding member 13is pivotally fastened to the cam'j` follower bar 8 by meansof pivot bolt12 and is received in the stitch settling guide 14. The latter isrotatably journalled by means of shaftY screw 15 and guide sleeve.' 16in the standard 2 whichhasarecess 17 forthat pur-V pose. The guide 14isprovided with an arm ,18 ,toY which the draw bar 20 ispivotallyconnected by'means. of shoulder screw 19. ,v

The lug 21 ofthe base plate 1 pivotally'supports thefeeder lift shaft,22' which is connected in the usual4` manner by way of crank 23 and cambar 24-to thev lifting cam (not shown) which is mounted von-the arin`shaft 5.

In accordance ,withthe invention the machine'is provided on'the frontside of the standard 2. with a molded1 conformation 25 which 'isprovided with a bore26` in'. which a bearing sleeve 27 issecurely'mounted. A hollow switching shaft 28 Ais Arotatablyreceiigledin sleeve '27 andJ presents at` its end 'which projects 'fromthe'standard 2 a kn'ob 29 and has at its other end which extends intothe standard 2 secured to it a socket 31 having a disk 32 by means of ascrew 30.' The disk 32 is provided with a recess 33 presenting outer andinner curved edges 34 and 35, respectively, as related to the axis ofrotation.

A disk 36 having a crimped border is secured by means of screws 37 inbores 38 in standard 2 between the operating knob 29 and theconformation 25 on the standard 2. The disk 36 and the knob 29 areprovided with markings for settings (not shown in the drawing). Bores 39in knob 29 serve for the insertion of screws 37 and are covered by acountersunk disk 40.

A crank shaped supporting arm 41` is provided on bearing sleeve 27 andis secured against turning by screws 42 (Fig. 4). The supporting arm 41extends through an aperture 43 in the wall into the interior of thestandard 2. A bolt 44 is provided at the free end of arm 41 whichsupports a contact lever 46 having a hub 45 and which is held in placeby a lock ring 47. Lever 46' presents an abutment or follower in theform of a stud 48 (Fig. 3) which extends into the recess 33 of disk 32.

The free end 49 of lever 46 extends at an angle and is pivotallyconnected to the draw bar 20 by means of a collar screw 50. 4 l

The stitch setting guide 14 (Fig. 2) has still a further arm 51 which isprovided With a bore 52 which is en- ,gaged by one end of a spring 53,the iother end of which is secured to a strap 54 which is hooked to anopening 55 in a recess 56 lof the standard. The spring 53 tends to biasthe stitch setting guide 14 in such a manner that the stud 48 on thelever 46 engages the curved edge 34 for the forward stitch on the disk32.

A pin 57 is secured to the offset end 49 of lever 46 which extends intothe plane' of rotation of a setting member 59 which is secured to amember 60 (Fig. 2). The latter is held in place by means of a screw 61upon a stitch setting shaft 62 which is journalled in the hollowswitching shaft 28. The free end of the shaft 62 is provided with a knobThe setting member 59 is biased by a spring 64 (Figs. 3

:and 4) which 'is hooked atone end into a 'bore 65 of a second lever arm66 and at the other end into a groove 67 in stud 44 whereby it isVturned counterclockwise to such an extent (as seen in Fig. 3) that itsthird lever arm 68 engages the reduced studend 69. y

The desired stitch length is set by rotating the switching knob 29 whichcauses the stud 48 to slide along the outer arcuated edge 34, becausethe contact lever 46 is pulled upwardly by spring 53 by way of draw bar20 and Stitchsetting guide V14. The outer curved edge 34 is formed in amanner that the distance from the point of rotation of the disk 32increases continuously when the disk is turned clockwise.Suitableforming of curved edge 34 permits of predetermining the increaseof the stitch length in relation .to the angle of rotation to be thesame or as otherwise desired. t

For setting the corresponding back stitch of the same size, knob 63 isturned clockwise (as see in Fig. 3) against the action `of spring 64until lever 46 is pressedvdownwardly by the arm 58 of the .settingmember 59 until the stud 48 engages `the curved back stitch edge 35. Thecurved edgev 35 is inversely related to the curved forward stitch edge34 withreference to a neutral circle which is concentric With respect tothe axis of rotation of the disk 32. Releasing manipulator knob 63results in return of setting member 59 under the pressure of spring 64to its initial position, while stud 48 is again brought into engagementwith the forward stitch edge 34.

What is claimed is:

l. Stitch adjusting mechanism for sewing machines of the type comprisinga main shaft including cam means, a feeder advancing shaft and a feederraising shaft, follower bars operatively connecting said advancing shaftand said raising shaft, respectively, to said main shaft, a stitchsetting guide connected to said follower bar for said advancing shaftand a draw bar operatively connecting said guide and said stitchadjusting mechanism, said mechanism including setting shaft extendingthrough the housing of the sewing machine a contact lever connected tosaid draw bar having a follower member, a disk concentric With saidsetting shaft extending in a plane perpendicularly to said shaft andpresentingan aperture receiving said follower member for guiding saiddraw bar, said aperture being defined by a pair of curved edgesextending in said plane at radial distances from the axis of rotation ofsaid disk in inverse relationship to one another and relative to aconcentric neutral arc.

2. Stitch adjusting mechanism in accordance with claim l, wherein saiddisk is secured to a sleeve journalled in the wall of said machinehousing and said setting shaftis received in said sleeve.

3. Stitch adjusting mechanism as set forth in claim 2 including a springbiasing said contact lever against one of said curved edges andextending between said housing and said setting guide, and a settingmember secured to said stitch setting shaft having an arm operativelyengaging said Contact lever by way of a stud provided on said contactlever.

4. Stitch adjusting mechanism in accordance with claim 3 wherein saidstitch setting shaft is provided with a turning knob and is springbiased by means of a return spring adapted to maintain said arm ininoperative position upon release of said knob.

References Cited in the le of this patent UNITED STATES PATENTS

